Support from nursing managers and administrators, together with the role of a dedicated project Lead, are consistently identified as important strategies for nurses to be able to use research evidence in their practice. However, little is known about the key behaviours and activities required to successfully implement and sustain research-based innovations in practice. This study describes the leadership behaviours and activities that influenced nurses' use of clinical practice guidelines. A secondary analysis of qualitative data was conducted to investigate factors that contributed to sustaining (or not) the use of clinical guidelines two and three years after implementation as part of the Registered Nurses Association of Ontario Best Practice Guidelines project. Grounded theory techniques were used to develop a theoretical model of Leadership. Findings indicated a different pattern of leadership in organizations that sustained guidelines, when compared to those that did not. Three broad leadership strategies emerged as central to successfully implementing and sustaining guidelines: (1) facilitating staff to use the guidelines, (2) creating a positive milieu of best practices and (3) influencing organizational structures and processes. Leadership for guideline implementation was found to include such behaviours as support, role-modelling commitment and reinforcing organizational policies and goals consistent with evidence-based care.